An Enhanced Throwback Story: Post-Tension Slab Drilling and 130 Cores

Job site showing rebar conduit before a concrete slab is poured

Post-tension slab drilling, cutting, and coring can be incredibly dangerous. Not only is there a risk of structural collapse, but you also risk severe injury and death. It’s definitely NOT something you want to play around with.

But what happens when you need to drill into post-tension concrete (also called PT concrete)? We had a project where the company needed to do just that.

The Job Site

Before the recession, a company bought three lots on one road. They built condos on the center lot with a parking garage underneath. Just as they finished pouring slabs on the parking garage of the two remaining lots, the recession hit.

So, they put tar paper and sod over the parking garages and turned them into parks. They left them like this for over five years until they were ready to resume with the original project.

The company wanted to build condos on one of the lots, with drastic changes to the original layout. It had been nearly six years since the project first began, so the new design makes sense. But the concrete had already been sleeved, and they wanted to move everything.

That presented a big challenge: They needed to core drill 130 holes all over this post-tensioned concrete. Now, post-tension cables are great because they allow concrete slabs to be thinner and more stable. But these cables are like rubber bands inside of concrete, and if you accidentally cut one, it can snap.

When you’re engaging in post-tension slab drilling, cutting, or coring you want to avoid this snap at all costs. It has the potential to cause serious injury or death. The rule is you aren’t supposed to cut these PT cables after they’re installed. Ideally, you would place sleeves in the forms before the concrete is poured, thereby avoiding the need to risk cutting a PT cable. 

Except sometimes your plans change.

Our customer needed to core 130 cores through a PT deck, so he called us.

The Project: Scanning Ahead of 130 Coring Locations 

Using our 1.6 GHz GPR antenna, we scanned every proposed coring location. This customer didn’t care about cutting embedded conduits — avoiding a PT cable hit was their only concern.

We meticulously scanned each area where the customer planned to core, taking time to make sure it was safe. In some cases, they were cleared to drill right where they wanted. But more often than not, they had chosen a spot right where a PT cable was sitting!

When we came across a section with a PT cable underneath, we indicated the spot with marks on the concrete and then found them an alternative spot to core nearby. The exchange usually sounded something like: “There’s PT cable here, here, and here, but if we move the core eight inches to the left, you’re in the clear.”

Image showing mark-ups over PT concrete prior to post-tension slab drilling

After our work was done, it was time for some serious post-tension slab coring.

The Results of Post-Tension Slab Coring x 130 Cores

Of course, when it’s time to actually do the post-tension slab coring, everyone gets (understandably) nervous because hitting a PT cable could be a matter of life or death. But there was no need to fret. In the end, not one single cable was cut or even nicked!

It was a 100% perfect job. That’s right! No hits. Zero near-misses. Zero downtime. 

The customer was extremely happy with our attention to detail. They expected to at least nick a cable or two, but they had never worked with Enhanced Scanning before.

Here, we take things like cutting through a post-tensioned slab very seriously. We pay attention to the small details and understand how important our level of care is to your project… and to the health and safety of your workers! We’re thorough, disciplined, and focused on every single job we do.

Even if you’re the last job on a Friday afternoon, we’ll never skimp on professionalism or attention to detail. It’s just too critical. Contact us today for help avoiding hits when cutting, coring, or drilling post-tensioned slab (or any other type).

Give us a call: So Cal - 951-783-2483 KC, MO - 816-693-6614